1. Field of the Invention
The present invention relates generally to switching systems for communications networks, and more specifically to a switching system for local telephone exchanges that directly serve subscribers and provide special service features.
2. Description of the Related Art
Japanese Laid-Open Patent Specification Hei-4-97645 discloses a service control point (SCP) of a signaling network for common channel interoffice signaling. The service control point has an interface to a communications network with which the signaling network is associated. It receives a service request via the interface from a switching system of the communications network and supplies the request to an application controller, which accesses a service specification table to read a service component for the requested service. Instructions will then be sent from the service control point to the originating switching system to set up the requested service through the communications network.
Japanese Laid-Open Patent Specification Hei-7-250164 discloses a switching system for a communications network. In the prior art system (FIG. 1), a call processor 10 receives call requests either from line interface 12 or trunk interface 13 to establish a connection through a switching network 11 between two subscribers or between a subscriber and an inter-office trunk. During the process of a call from a subscriber, an event analyzer 14 analyzes the status of the call to detect an event (e.g., hook flashes) for triggering a corresponding service feature. In response to the detection of an event, a service controller 15 makes a search through a service registration memory 16 for all service features that can be combined and provided to the subscriber as a composite service with respect to that event to receive programmed instructions of the composite service. Service controller 15 then accesses an event-specific priority memory 17 to determine the priorities of the individual service features of the composite service. Service-specific scheduling memories 18 are provided to indicate for each service feature a following service feature to be executed next. Service controller 15 references the scheduling memories according to the determined priorities and makes a decision on whether to proceed to provide the following service feature. Programmed instructions of the service features which are determined to be provided to the subscriber are supplied from the service controller to the call processor.
However, the service controller is required to make decisions by taking into account all possibilities chat can be encountered before it command the call processor to execute programmed instructions. Therefore, the prior art adds to system complexity, which results in difficulty for engineering design and maintenance.